Use of the Regex class for C # regular expressions

C # provides a very powerful function for the use of regular expressions, which is the Regex class. This package is included under the System.Text.RegularExpressions namespace, and the DLL where the namespace is located basically does not need to be added separately in all project templates and can be used directly.

1. Define an instance of a Regex class

Regex regex = new Regex (@ "\d");
The initialization parameter here is a regular expression, and "\d" represents the configuration number.

2. Whether the match is judged

Determines whether a string matches a regular expression, and in a Regex object, you can use the Regex.IsMatch (string) method.

Regex. IsMatch ("abc"); The return value is False, the string does not contain a number
Regex. IsMatch ("Abc3abc"); The return value is true because the string contains a number

3. Get the number of matches

Use the Regex.Matches (string) method to get a Matches collection, and then use the Count property of this collection.

Regex. Matches ("Abc123abc"). Count;
The return value is 3 because the number is matched three times.

4. Get the matching content

Use the Regex.match (string) method to match.

Regex. Match ("Abc123abc"). Value;
A return value of 1 indicates the first match to the value.

5. Capture

You can use parentheses to capture part of a value in a regular expression, and to get the captured value, you can Regex.match (string). Groups[int]. Value to obtain.

Regex regex = new Regex (@ "\w (\d*) \w"); Matches a two-letter string of numbers
Regex. Match ("Abc123abc"). Groups[0]. Value; The return value is "123".

usingSystem; usingSystem.Text.RegularExpressions; namespaceMagci.Test.Strings { Public classTestregular { Public Static voidWritematches (stringstr, matchcollection matches) {Console.WriteLine ("\nstring is:"+str); Console.WriteLine ("No. of matches:"+matches.                          Count); foreach(Match NextMatchinchmatches) {                                  //Take out a matching string and up to 10 peripheral characters                intIndex =Nextmatch.index; stringresult =nextmatch.tostring (); intCharsbefore = (Index <5) ? Index:5; intFromend = str. Length-index-result.                                  Length; intCharsafter = (Fromend <5) ? Fromend:5; intCharstodisplay = Charsbefore + result. Length +Charsafter; Console.WriteLine ("Index: {0},\tstring: {1},\t{2}", Index, result, str. Substring (Index-Charsbefore, Charstodisplay)); }                  }                            Public Static voidMain () {stringSTR =@"My name is MAGCI, for short MGC. I like C sharp!"; //find "GC"            stringPattern ="GC"; MatchCollection Matches= Regex.Matches (Str, Pattern, Regexoptions.ignorecase |regexoptions.explicitcapture);                                        Writematches (STR, Matches); //find words that begin with "M" and End With "C"Pattern =@"\bm\s*c\b"; Matches= Regex.Matches (Str, Pattern, Regexoptions.ignorecase |regexoptions.explicitcapture);                  Writematches (STR, Matches); }          }  } 

Use of the Regex class for C # regular expressions